High self-opening rate refined channel sand and preparation method thereof

Abstract

This application relates to the technical field of sprue tapping sand, specifically disclosing a high self-opening rate refined sprue tapping sand and its preparation method. The high self-opening rate refined sprue tapping sand comprises the following raw materials in parts by weight: 65-75 parts chromite sand; 10-25 parts quartz sand; 3-7 parts sprue sand; 0.5-1 part carbon black; 0.5-1 part graphite; and 0.05-0.1 parts binder. The sprue tapping sand of this application can be used for refining ladle nozzles, possessing good fluidity, a low coefficient of thermal expansion, and appropriate bulk density. It also has the advantages of a suitable sintered layer thickness, strong resistance to seepage and erosion, and the ability to effectively improve the automatic opening rate of the ladle.

Description

Technical Field

[0001] This application relates to the technical field of diversion sand, and more specifically, it relates to a high self-opening rate refined diversion sand and its preparation method. Background Technology

[0002] Automatic ladle pouring refers to the process where molten steel flows out of the ladle automatically after the sliding gate is opened. The amount of effluent used for effluent pouring directly affects the automatic pouring rate. If automatic pouring is not possible and oxygen is used for effluent pouring, not only are there safety hazards, but production efficiency is also affected. This results in open pouring of molten steel, causing secondary oxidation and impacting the quality of the cast billet.

[0003] Currently, there are four main types of casting sand used domestically and internationally: siliceous, chromium-based, magnesia-based, and zirconium-based. Siliceous casting sand uses quartz sand as its base material. When the SiO2 content is above 93%, the self-opening rate of siliceous casting sand is significantly affected by the steel's holding time and refining time; generally, a longer refining time leads to a lower self-opening rate. Chromium-based casting sand mainly uses chromite sand. This type of casting sand has high refractoriness and strong impermeability, maintaining a high self-opening rate even after a long steel settling time. However, chromite sand raw materials are mainly imported, resulting in high costs and susceptibility to resource constraints. Magnesia-based casting sand uses forsterite and magnesia as its main raw materials, and its self-opening rate is also relatively low during continuous casting. Zirconium-based casting sand's main raw material is zircon sand; due to its high price, although it has a high self-opening rate, its application is limited.

[0004] To reduce the cost of the sprue sand, chromium sprue sand was used instead of zirconium sprue sand, and a certain proportion of quartz sand was added to the chromium sprue sand. However, when the refining time of the ladle is long or when refining low alloy steel, the sprue sand is exposed to the high temperature of the molten steel for a longer period of time, which leads to a thicker sintered layer in the ladle nozzle. This is not conducive to the molten steel breaking through the sintered layer, resulting in a decrease in the self-opening rate. Summary of the Invention

[0005] In order to reduce the decrease in self-opening rate of the priming sand due to the long refining time, this application provides a high self-opening rate refined priming sand and its preparation method.

[0006] In the first aspect, this application provides a high self-opening rate refining guide sand, which adopts the following technical solution:

[0007] A high self-opening refining guide sand comprises the following raw materials in parts by weight:

[0008] 65-75 parts of chromite sand;

[0009] 10-25 parts of quartz sand;

[0010] 3-7 parts of pearl powder;

[0011] Carbon black 0.5-1 part;

[0012] 0.5-1 part graphite;

[0013] 0.05-0.1 parts of binder.

[0014] By adopting the above technical solutions, the combined use of chromite sand and quartz sand can improve the high cost of using chromite sand alone; by adjusting the dosage of quartz sand and chromite sand, the low self-opening rate of quartz sand can be overcome; spherical abrasive sand, being spherical particles, can improve the fluidity of the guiding sand; the addition of carbon black and graphite as regulators helps reduce the penetration of high-temperature molten steel; and the addition of binders to wet the surfaces of chromite sand, quartz sand, and spherical abrasive sand further facilitates the adhesion of carbon black and graphite, giving the guiding sand a lower thermal expansion coefficient, higher refractoriness, and better impermeability, thereby improving the self-opening rate.

[0015] Preferably, the quartz sand is a composite quartz sand with a zirconium dioxide layer coated on its surface.

[0016] By adopting the above technical solution, since quartz sand has a low specific gravity, it is easy to float under the action of steel flow. Furthermore, siliceous duct sand (i.e., quartz sand) has the disadvantages of high expansion rate and relatively low melting point. Under the long-term high temperature of the steel ladle, it is easy to cause the sintering layer to be too thick, thereby reducing the automatic casting rate.

[0017] By modifying the quartz sand to coat its surface with a zirconium dioxide layer, the floating of the quartz sand under the action of the steel flow during tapping is reduced. Furthermore, since zirconium dioxide transforms from a monoclinic crystal form to a tetragonal crystal form under high temperature conditions, accompanied by volume shrinkage, the volume expansion of the quartz sand is accompanied by the volume shrinkage of the zirconium dioxide, allowing the two to remain tightly bonded together at high temperatures. On the one hand, this can counteract the sintering of the guide sand against the sidewall of the ladle nozzle due to volume expansion. On the other hand, due to the presence of zirconium dioxide, the quartz sand particles are less likely to form an excessively thick sintering layer under prolonged high-temperature conditions, thus ensuring a good self-opening rate.

[0018] Preferably, the preparation steps of the composite quartz sand with a zirconium dioxide layer on the surface are as follows:

[0019] Step A1: Disperse unmodified quartz sand in anhydrous ethanol;

[0020] Step A2: Add water and zirconium isopropoxide sequentially, with a weight ratio of zirconium isopropoxide to water of 1:(2-3). React under reflux for 1.5-2 hours. After the reactants are cooled to room temperature, centrifuge and wash the product. Repeat this step 2-3 times to obtain the product.

[0021] Step A3: The obtained product is heat-treated at 500℃-600℃ to obtain quartz sand coated with a zirconium dioxide layer.

[0022] By employing the above technical solution, a zirconium dioxide layer is deposited on the surface of quartz sand through the hydrolysis and condensation of zirconium isopropoxide, resulting in zirconium dioxide-coated composite quartz sand. Since the hydrolysis reaction of zirconium isopropoxide is exothermic, it can be carried out on the surface of the quartz sand without heating. After repeating step A2 2-3 times and undergoing high-temperature heat treatment, the resulting zirconium dioxide coating thickness allows for better synergistic interaction with the quartz sand. In the long-term high-temperature environment of the ladle, the guiding sand exhibits an appropriate degree of sintering, enabling the molten steel to successfully break through the sintered layer and achieve self-opening, thus improving the self-opening rate.

[0023] Preferably, the particle size of the composite quartz sand with a zirconium dioxide layer on its surface is 700-900 micrometers.

[0024] By adopting the above technical solution, when the particle size of the composite quartz sand coated with zirconium dioxide is within this range, it has better flow properties, which can reduce the problem of excessively thick sintered sand layer, and the expansion rate is low, thereby improving its self-opening rate. When the particle size of the composite quartz sand is too small, over-sintering is likely to occur. When the particle size of the composite quartz sand is too large, uneven mixing is likely to occur, resulting in the inability to form a good bulk density.

[0025] Preferably, it also includes 0.5-1 part of calcium oxide.

[0026] By adopting the above technical solution, adding calcium oxide during the use of diversion sand can also provide an alkaline environment, reduce the phenomenon of slag adhesion at the ladle nozzle, thereby ensuring the flow effect of the diversion sand and improving the self-opening rate.

[0027] Preferably, the binder is water.

[0028] By adopting the above technical solution and adding water as a binder, the surface of the raw material of the guiding sand can be wetted, so that the trace powdery raw materials such as graphite and carbon black can better adhere to the particle surface and reduce segregation. In addition, the surface of calcium oxide particles can release heat after contacting water. On the one hand, it reduces the freezing situation when mixing in cold winter environments. On the other hand, the water can be quickly discharged after the raw materials are mixed, shortening the drying time of the guiding sand.

[0029] Secondly, this application provides a method for preparing high self-opening rate refining guide sand, which adopts the following technical solution:

[0030] A method for preparing high self-opening rate refining guide sand includes the following steps:

[0031] First, put chromite sand and quartz sand into a mixing equipment and mix for 2-3 minutes. Then add jewel sand and mix for 2-3 minutes. Next, add binder and mix for 2-3 minutes. Finally, add carbon black, graphite and calcium oxide and stir for 1-2 minutes to obtain a mixture. Bake the mixture at 170℃-200℃ for 1-2 hours to obtain diversion sand.

[0032] By adopting the above technical solution, chromite sand is mixed evenly with quartz sand and alumina sand before adding a binder. The amount of binder is controlled to only wet the surface of the raw material particles, which helps the carbon black, graphite and calcium oxide to combine. The baking process dries the moisture and reduces the occurrence of boiling when the water-containing guide sand comes into contact with the molten steel.

[0033] Preferably, the particle size of the diversion sand is no greater than 1.25 mm.

[0034] By adopting the above technical solution, the particle size of the produced diversion sand product is no greater than 1.25mm, ensuring that it has good fluidity and low thermal expansion rate and bulk density, thereby improving the automatic start-up rate.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. Since this application uses spherical sand, which consists of spherical particles, it can improve the flowability of the diversion sand.

[0037] 2. In this application, composite quartz sand with a zirconium dioxide layer is preferably used to reduce the floating of quartz sand under the action of the steel flow during tapping. Furthermore, since zirconium dioxide transforms from a monoclinic crystal form to a tetragonal crystal form under high temperature conditions and is accompanied by volume shrinkage, the volume expansion of quartz sand is accompanied by the volume shrinkage of zirconium dioxide, so that the two can still be tightly bonded together at high temperature. On the one hand, this can counteract the sintering of the guide sand against the side wall of the ladle nozzle due to volume expansion. On the other hand, due to the presence of zirconium dioxide, the quartz sand particles are not prone to forming an excessively thick sintering layer under long-term high temperature conditions, thereby ensuring a good self-opening rate.

[0038] 3. The method of this application involves mixing chromite sand with quartz sand and alumina sand evenly before adding a binder. The amount of binder is controlled so that it only wets the surface of the raw material particles, thereby facilitating the bonding of carbon black, graphite and calcium oxide. Detailed Implementation

[0039] Raw material source:

[0040] The particle size of the chromite sand is 30-40 mesh, and its composition is as follows:

[0041] Element <![CDATA[Cr2O3]]> <![CDATA[SiO2]]> CaO <![CDATA[Fe2O3]]> index ≥46％ <1％ ≤0.5％ <29％

[0042] Quartz sand has a particle size of 30-40 mesh, and its main component is silicon dioxide;

[0043] The particle size of the granulated sand is 30-40 mesh, the refractoriness is ≥1790℃, and the bulk density is 1.95-2.05 g / cm³. 3 Its composition includes Al2O3: 65-80%, SiO2: 10%-20%, TiO2≤3.5%;

[0044] Carbon black CAS number: 1333-86-4;

[0045] Graphite CAS No.: 7782-42-5;

[0046] Zirconium isopropoxide CAS No.: 2171-98-4; Molecular weight: 327.572;

[0047] Calcium oxide CAS number: 73018-51-6;

[0048] Magnesium oxide CAS number: 1309-48-4.

[0049] Example

[0050] Examples 1.1-1.3

[0051] A high self-opening refining guide sand comprises the following raw materials by weight:

[0052] Chromium ore sand 65-75kg;

[0053] 10-25 kg of quartz sand;

[0054] 3-7 kg of pearl powder;

[0055] Carbon black 0.5-1kg;

[0056] Graphite 0.5-1kg;

[0057] 0.05 kg of binder.

[0058] The raw material usage for Examples 1.1-1.3 is shown in Table 1.

[0059] Table 1. Raw material consumption (unit: kg) for Examples 1.1-1.3

[0060]

[0061]

[0062] The binder is water.

[0063] A method for preparing high self-opening rate refining guide sand includes the following steps:

[0064] First, put chromite sand and quartz sand into a mixing equipment and mix for 3 minutes. Then add jewel sand and mix for 3 minutes. Next, add binder and mix for 3 minutes. Finally, add carbon black and graphite and stir for 2 minutes to obtain a mixture. Bake the mixture at 200°C for 2 hours to obtain diverting sand.

[0065] Example 2

[0066] A high self-opening rate refining guide sand differs from Example 1.2 in that an equal amount of composite quartz sand coated with a zirconium dioxide layer replaces the quartz sand, wherein the particle size of the composite quartz sand is 900 micrometers.

[0067] The preparation method of composite quartz sand coated with a zirconium dioxide layer includes the following steps:

[0068] Step A1: Disperse 20 kg of unmodified quartz sand in anhydrous ethanol;

[0069] Step A2: Add 20 kg of zirconium isopropoxide and water in sequence, with a weight ratio of zirconium isopropoxide to water of 1:(2-3). React under reflux for 2 h. After the reactants are cooled to room temperature, centrifuge them and wash them with anhydrous ethanol. Repeat this reaction step 3 times to obtain the product.

[0070] Step A3: The obtained product is heat-treated at 600℃ to obtain composite quartz sand coated with a zirconium dioxide layer.

[0071] Examples 3.1-3.3

[0072] A high self-opening refined effluent sand differs from Example 2 in that the composite quartz sand coated with a zirconium dioxide layer has a different particle size.

[0073] The composite quartz sand in Example 3.1 has a particle size of 700 micrometers. In the process of preparing the composite quartz sand, step A2 is repeated twice.

[0074] In Example 3.2, the particle size of the composite quartz sand is 550 micrometers, and step A2 is repeated once during the preparation of the composite quartz sand.

[0075] In Example 3.3, the particle size of the composite quartz sand is 1000 micrometers, and step A2 is repeated 4 times during the preparation of the composite quartz sand.

[0076] Example 4

[0077] A high self-opening rate refining guide sand differs from Example 2 in that an equal amount of composite quartz sand coated with a magnesium oxide layer is used instead of composite quartz sand coated with a zirconium dioxide layer.

[0078] The preparation steps of composite quartz sand coated with magnesium oxide are as follows: unmodified quartz sand is dispersed in anhydrous ethanol and then magnesium oxide is added. The weight ratio of magnesium oxide to quartz sand is 1:1. The temperature is raised to 100℃ and reacted under reflux for 2 hours. After the reactants are cooled to room temperature, the products are centrifuged, washed and dried to obtain composite quartz sand coated with magnesium oxide.

[0079] Examples 5.1-5.3

[0080] A high self-opening rate refining guide sand, which differs from Example 2 in that it also contains 0.5-1 kg of calcium oxide.

[0081] In Example 5.1, the amount of calcium oxide added was 0.5 kg;

[0082] In Example 5.2, the amount of calcium oxide added was 0.8 kg;

[0083] In Example 5.3, the amount of calcium oxide added was 1 kg.

[0084] A method for preparing high self-opening refining guide sand includes the following steps:

[0085] First, put chromite sand and quartz sand into a mixing equipment and mix for 3 minutes. Then, add jewel sand and mix for 3 minutes. Next, add a binder and mix for 3 minutes. Finally, add carbon black, graphite and calcium oxide and stir for 2 minutes to obtain a mixture. Bake the mixture at 170°C for 1 hour to obtain diversion sand.

[0086] Example 6

[0087] A high self-opening refining guide sand, which differs from Example 5.2 in that an equal amount of sodium oxide is used instead of calcium oxide.

[0088] Comparative Example 1

[0089] A high self-opening rate refined guide sand, which differs from Example 1.2 in that the amount of pearl sand used is 0 kg.

[0090] Comparative Example 2

[0091] A high self-opening rate refined diversion sand, which differs from Example 1.2 in that it uses a commercially available chromium diversion sand product.

[0092] Performance testing

[0093] The tests include:

[0094] 1. Angle of Repose Test

[0095] The angle of repose is the angle formed by the intersection of the surface of a stationary sample and the horizontal plane. Its size directly reflects the flow properties of the sample. The smaller the angle of repose, the smaller the coefficient of friction of the sample and the better the flow properties.

[0096] The measuring apparatus consists of a support, a funnel, a circular plate, and a ruler. A certain amount of diverting sand sample is poured into the funnel, allowing the sand to flow through the funnel and fall onto a circular plate with a diameter of 200 mm. The angle of repose is then determined based on the flow value.

[0097] 2. Bulk density test

[0098] By placing a certain mass of diverting sand in a weighing container and measuring its bulk density under standard vibration conditions, the compaction and bulk density of the diverting sand are determined to determine whether they meet the requirements.

[0099] 3. Sintering performance test

[0100] The strength of the samples after firing is used to represent the sintering properties. Standard samples of the guiding sand are prepared and fired at 1750℃ for 6 hours. After cooling, the strength of the samples is measured. The flexural strength of the fired samples characterizes the sintering properties of the guiding sand at high temperatures. This allows for accurate determination of whether the guiding sand can be crushed and self-opened under the hydrostatic pressure of molten steel. A higher flexural strength after sintering indicates a lower self-opening rate.

[0101] The angle of repose, bulk density and sintering performance of the diversion sands of Examples 1.1-1.3 and Comparative Examples 1-2 were tested respectively, and the test results are shown in Table 2.

[0102] Table 2 shows the test results for Examples 1.1-1.3 and Comparative Examples 1-2.

[0103] Example 1.1 Example 1.2 Example 1.3 Comparative Example 1 Comparative Example 2 Angle of repose / (°) 25 23 25 31 30 Bulk density (g / 100ml) 238 237 237 228 220 Flexural strength after sintering (MPa) 9.3 9.1 9.5 16 15

[0104] As can be seen from Examples 1.1-1.3 and Comparative Examples 1-2, and Table 2, this application overcomes the problem of low self-opening rate of quartz sand by adjusting the amount of quartz sand and chromite sand; the addition of spherical abrasive sand improves the fluidity of the guiding sand; the addition of carbon black and graphite as regulators helps reduce the penetration of high-temperature molten steel; the addition of binder wets the surfaces of chromite sand, quartz sand, and spherical abrasive sand, further facilitating the adhesion of carbon black and graphite, resulting in a lower thermal expansion rate and higher refractoriness of the guiding sand, thus improving the self-opening rate.

[0105] Examples 2, 3.1-3.3, and 4 were tested for angle of repose, bulk density, and sintering performance. The test results are shown in Table 3.

[0106] Table 3 Test results of Examples 2, 3.1-3.3, and 4

[0107] Example 2 Example 3.1 Example 3.2 Example 3.3 Example 4 Angle of repose / (°) 18 17 22 21 25 Bulk density (g / 100ml) 246 243 239 238 237 Flexural strength after sintering (MPa) 7.8 7.9 8.9 8.6 13

[0108] Combining Examples 2 and 1.2 with Tables 2-3, it can be seen that when the added quartz sand is composite quartz sand coated with a zirconium dioxide layer, the high density of zirconium dioxide makes it difficult for the quartz sand to float in the ladle. Furthermore, under prolonged high-temperature conditions, the quartz sand and zirconium dioxide undergo volume expansion and contraction due to temperature, allowing them to remain tightly bonded together at high temperatures. On the one hand, this counteracts the sintering of the guide sand against the sidewall of the ladle nozzle due to volume expansion. On the other hand, due to the presence of zirconium dioxide, the quartz sand particles are less likely to form an excessively thick sintering layer under prolonged high-temperature conditions, thus ensuring a good self-opening rate.

[0109] Combining Examples 2 and 3.1-3.3 with Table 2, it can be seen that Examples 2 and 3.1 are superior to Examples 3.2-3.3. This indicates that during the preparation of composite quartz sand coated with a zirconium dioxide layer, when the particle size of the composite quartz sand is 700-900 micrometers, it has good flow properties and self-opening rate. When the particle size of the composite quartz sand is too small (as in Example 3.3), over-sintering is likely to occur; when the particle size of the composite quartz sand is too large (as in Example 3.4), uneven mixing is likely to occur, resulting in the inability to form a good bulk density, which in turn leads to a higher permeability of the molten steel to the guiding sand, increasing the thickness of the sintered layer.

[0110] Combining Examples 2 and 4 with Tables 2-3, it can be seen that Example 2 is significantly superior to Example 4. The reason for this is that the zirconium dioxide layer deposited on the surface of the quartz sand is wrapped with it. Under high temperature conditions, the zirconium dioxide layer undergoes volume expansion and contraction, which makes the wrapped zirconium dioxide layer discontinuous, causing some quartz sand to leak out on the surface. However, the zirconium dioxide layer does not detach from the quartz sand, resulting in good sintering degree and avoiding the problem of excessive sintering leading to thickened sintered layer and reduced self-opening rate. In contrast, when using composite quartz sand wrapped with magnesium oxide, both expand under high temperature conditions, which not only easily causes separation between the two but also increases the expansion rate of the guiding sand, resulting in excessive sintering and reduced self-opening rate.

[0111] The angle of repose and flexural strength of Examples 5.1-5.3 and Example 6 were tested, and the test results are shown in Table 4.

[0112] Table 4 Test results of Examples 5.1-5.3 and Example 6

[0113] Example 5.1 Example 5.2 Example 5.3 Example 6 Angle of repose / (°) 14 13 13 17 Flexural strength after sintering (MPa) 7.9 7.8 7.9 8.2

[0114] Combining the test results of Examples 2 and 5.1-5.3 and Tables 2 and 4, it can be seen that the flow effect of the guiding sand in Examples 5.1-5.3 is better than that in Example 2. Furthermore, the guiding sand maintains good fluidity and good sintering degree even with a shortened drying time during preparation, and improves the self-opening rate.

[0115] Combining Examples 5.2 and 6 with Table 4, it can be seen that adding calcium oxide to the guide sand can, on the one hand, provide an alkaline environment, reduce slag adhesion at the ladle nozzle, and thus ensure the flow effect of the guide sand and improve the self-opening rate. On the other hand, the surface of calcium oxide particles can release heat after contacting water, which can reduce the freezing situation when mixing in cold winter environments. Furthermore, the water can be quickly discharged after the raw materials are mixed, shortening the drying time of the guide sand. Sodium oxide is difficult to achieve the above effects simultaneously.

[0116] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high self-opening rate refining guide sand, characterized in that, The ingredients include the following parts by weight: 65-75 parts of chromite sand; 10-25 parts of quartz sand; 3-7 parts of pearl powder; Carbon black 0.5-1 part; 0.5-1 part graphite; 0.05-0.1 parts of binder; The quartz sand is a composite quartz sand with a zirconium dioxide layer coated on the surface; The preparation steps of the composite quartz sand with a zirconium dioxide layer on the surface are as follows: Step A1: Disperse unmodified quartz sand in anhydrous ethanol; Step A2: Add water and zirconium isopropoxide sequentially, with a weight ratio of zirconium isopropoxide to water of 1:(2-3). React under reflux for 1.5-2 hours. After the reactants are cooled to room temperature, centrifuge and wash the product. Repeat this step 2-3 times to obtain the product. Step A3: The obtained product is heat-treated at 500℃-600℃ to obtain quartz sand coated with a zirconium dioxide layer. The composite quartz sand with a zirconium dioxide layer on its surface has a particle size of 700-900 micrometers; It also includes 0.5-1 part calcium oxide; The binder is water.

2. A method for preparing high self-opening rate refining guide sand as described in claim 1, characterized in that, Includes the following steps: First, put chromite sand and quartz sand into a mixing equipment and mix for 2-3 minutes. Then add jewel sand and mix for 2-3 minutes. Next, add binder and mix for 2-3 minutes. Finally, add carbon black, graphite and calcium oxide and stir for 1-2 minutes to obtain a mixture. Bake the mixture at 170℃-200℃ for 1-2 hours to obtain diversion sand.

3. The method for preparing high self-opening rate refining guide sand according to claim 2, characterized in that, The particle size of the diversion sand is no greater than 1.25 mm.

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